add CDL query and fetch

[ircwaves]

• https://nassgeodata.gmu.edu/CropScape/devhelp/getexamples.html
• https://nassgeodata.gmu.edu/CropScape/devhelp/help.html

[bhbraswell]

The idea here is that we would use their WCS to request CDL data assets. A tile would still be defined as a state and identified by name of FIPS code. Fetch should be compatible with versioning as mentioned in the newly reopened #38